5,5,6-Trimethylbicyclo[2.2.1]heptan-2-one in the Synthesis of Carbocyclic Analogs of Prostaglandin Endoperoxides |
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Authors: | F S Pashkovskii F A Lakhvich S S Koval'skaya and N G Kozlov |
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Institution: | (1) National Academy of Sciences of Belarus, Institute of Bioorganic Chemistry, Minsk, Belarus;(2) National Academy of Sciences of Belarus, Institute of Physical Organic Chemistry, Minsk, Belarus |
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Abstract: | 1,3-Dipolar cycloaddition of nitrile oxides to 5,5,6-trimethyl-exo-2-ethynylbicyclo2.2.1]heptan-endo-2-ol yields the corresponding 2-(isoxazol-5-yl) derivatives. Opening of the isoxazole ring in the latter gives rise to prostanoid precursors with partially built up or completed side chain. 5,5,6-Trimethyl-3-methylenebicyclo2.2.1]heptan-2-one reacts with nitromethane in the presence of tetramethylguanidine to afford 5,5,6-trimethyl-exo-3-(2-nitroethyl)bicyclo2.2.1]heptan-2-one which can be converted into the corresponding nitrile oxide by the action of phenyl isocyanate in benzene in the presence of triethylamine as catalyst. 1,3-Dipolar cycloaddition of the nitrile oxide to ethyl 4-pentynoate yields 3-exo-5-(2-ethoxycarbonylethyl)isoxazol-3-ylmethyl]-5,5,6-trimethylbicyclo2.2.1]heptan-2-one. Treatment of the latter with hydroxyl amine leads to formation of the corresponding Z-oxime whose reaction with n-hexyl bromide results in transalkylation of the ester group to afford 3-exo-5-(2-hexyloxycarbonylethyl)isoxazol-3-ylmethyl]-5,5,6-trimethylbicyclo2.2.1]heptan-2-one oxime. |
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